1. Field of the Invention
The present invention relates to an apparatus for handling sheet materials, and more particularly to a sheet handling apparatus for effecting certain specified processes such as folding or stapling on sheets fed from a recording apparatus such as a copying or printing apparatus.
2. Related Background Art
There is already proposed a copying machine or a printing apparatus with stapling function for binding sheets by driving a staple, or a U-shaped metal strip, into the sheets.
Such stapling function is convenient for the users as the image recording and document binding are achieved at the same time.
In a sheet handling apparatus, such as a copying machine, with such stapling function, it is customary to employ a recycling document feeder (RDF) (also called recycling document handler (RDH)) and to effect the stapling each time when a recycling of the sheets on the RDF is detected.
However such stapling operation cannot be effected in case of automatic sheet-by-sheet feeding, because it is difficult to identify the completion of copying operation on all the documents.
Also in the above-mentioned sheet handling apparatus, the stapling operation is not possible or required complex procedure in case of the book copying mode in which the RDF or automatic document feeder (ADF) is not used, although such copying mode is often used. Also if the stapling mode is erroneously selected in case of a single copying, the obtained copy is usually stapled though it is in fact unnecessary.
Also in such apparatus, if the stapling function is selected when a sheet cassette of an irregular size or a manual sheet feeding is designated, the image recording or copying operation becomes prohibited, thus causing a trouble for the user.
Certain copying machines have an interruption copy mode in which a continuous copying operation can be interrupted for starting a copying operation of another mode, but such interruption copy mode is prohibited during the stapling operation, and such apparatus is therefore inconvenient for the users.
Also certain copying machines have an automatic paper selection (APS) function of detecting the original size and selecting a copy sheet according to the detected size. On the other hand, the stapling mode has a limitation that it is applicable only to the recording sheets of a same size. Thus, if a recording sheet not matching said limitation is selected for example from a cassette during the stapling mode, the entire apparatus has to be stopped. Thus the image recording itself is interrupted, and the mode setting has to be made anew after the staple mode is cancelled.
Also in the normal status, the stapling operation is conducted in response to the detection of the end of original documents on the RDF etc. as explained before. If necessary, the operator may interrupt the recording operation by actuating a stop key, but there will result an inconvenience in such case that the discharged copy sheets cannot be stapled.
Also in such apparatus there is already known a structure equipped with a staple tray for stacking sheets for stapling, and a stack tray for receiving stapled bundles of sheets.
However, in transporting a stapled sheet bundle from the staple tray to the stack tray, the stapled bundle is often not neatly placed on other sheet bundles already contained in the stack tray, or an uppermost sheet is disengaged from the staples, according to the size or the number of sheets in the bundle.
Furthermore, in such apparatus, the stapling mode may not provide the user with the desired set of copies but produce miscopies, to the disadvantage of the user, if the copies are made irrespective of the number of originals or preset copy number-and are unconditionally stapled.
Furthermore, in such apparatus, the succeeding image recording operation is prohibited during the stapling operation, and such prohibition may reduce the throughput of the entire recording operation.
Furthermore, in such apparatus, the stapling operation is conducted on the sheets stacked, after recording, on tray means provided in the apparatus. Thus, if the operator leaves some recording sheets on said tray and the next operator initiates a stapling operation utilizing the original feeding means and without removing such remaining sheets, such remaining sheets may be mixed in the sheets obtained in the succeeding operation.
Furthermore, in such apparatus, the operator can usually select a sorting mode or a grouping mode in which copies obtained from a same original are grouped, regardless whether the stapling mode is selected or not. However if the grouping mode is erroneously designated in combination with the stapling mode, the copies from a same original are stapled. This is apparently different from the properly collated copies which the user wishes. In this manner the conventional apparatus are difficult to operate and tend to provide erroneous copies.
Furthermore, in such apparatus, the stapling function is activated only when the sorting mode or the grouping mode is selected.
There are also already known certain apparatus capable of stapling function and folding function. Such folding function is usually achieved by a pair of folding rollers and by inserting a looped recording sheet into the nip of said folding rollers.
However the sheet handling apparatus with such folding mechanism may generate improper folding due to wrinkles in the sheet, skewed movement thereof, or dust or scars on the folding rollers, thus eventually leading a sheet jam in the downstream path. Even if such sheet jam does not occur, such improperly folded sheets, if stapled in such state, may require restapling or refolding.